Actually, I don't believe that organised religions are terribly destructive these days. And back when they were more destructive I think it was also true that societies themselves were more destructive. Despite its sometimes bad rep, I can't think of many cases where religion alone causes destructive social behaviours (though I think there may be some). More often I think it has taken advantage of, and directed those behaviours to its own benefit - and more often these days, I think it opposes those behaviours.
More than destructiveness, I take issue with some of the things that religions create and preserve: ignorance, delusion, inhumane and cruel beliefs. I feel that they create these things to help get people to submit to them, and they preserve them to hold their power. In consequence, they sometimes slow down improvements to society, distract and confuse people who are genuinely seeking knowledge, and people can suffer because of that.
Balanced against that I recognise that religion is a binding and often benign social force. I suppose that my biggest problem is that, for all the influence it sometimes wields, it is distressingly unaccountable - to itself, to society and to the people it is supposed to serve.